path: root/fs/cifs/connect.c
diff options
authorRonnie Sahlberg <lsahlber@redhat.com>2019-07-06 06:52:46 +1000
committerSteve French <stfrench@microsoft.com>2019-07-07 22:37:43 -0500
commitf2caf901c1b7ce65f9e6aef4217e3241039db768 (patch)
treec5f38dc1911eb2286937c8137bbec59a08962b32 /fs/cifs/connect.c
parentcifs: always add credits back for unsolicited PDUs (diff)
cifs: Fix a race condition with cifs_echo_request
There is a race condition with how we send (or supress and don't send) smb echos that will cause the client to incorrectly think the server is unresponsive and thus needs to be reconnected. Summary of the race condition: 1) Daisy chaining scheduling creates a gap. 2) If traffic comes unfortunate shortly after the last echo, the planned echo is suppressed. 3) Due to the gap, the next echo transmission is delayed until after the timeout, which is set hard to twice the echo interval. This is fixed by changing the timeouts from 2 to three times the echo interval. Detailed description of the bug: https://lutz.donnerhacke.de/eng/Blog/Groundhog-Day-with-SMB-remount Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com> Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com> Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to '')
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index f1061e6579e4..1eb73149e6d4 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -706,10 +706,10 @@ static bool
server_unresponsive(struct TCP_Server_Info *server)
- * We need to wait 2 echo intervals to make sure we handle such
+ * We need to wait 3 echo intervals to make sure we handle such
* situations right:
* 1s client sends a normal SMB request
- * 2s client gets a response
+ * 3s client gets a response
* 30s echo workqueue job pops, and decides we got a response recently
* and don't need to send another
* ...
@@ -718,9 +718,9 @@ server_unresponsive(struct TCP_Server_Info *server)
if ((server->tcpStatus == CifsGood ||
server->tcpStatus == CifsNeedNegotiate) &&
- time_after(jiffies, server->lstrp + 2 * server->echo_interval)) {
+ time_after(jiffies, server->lstrp + 3 * server->echo_interval)) {
cifs_dbg(VFS, "Server %s has not responded in %lu seconds. Reconnecting...\n",
- server->hostname, (2 * server->echo_interval) / HZ);
+ server->hostname, (3 * server->echo_interval) / HZ);
return true;